The present invention is directed to the nitrogenation of hydrocarbons, preferably of unsaturated hydrocarbons.
More particularly, the process of the present invention is directed to the nitrogenation of hydrocarbons in order to produce cyclic imides and dinitriles. Preferably, unsaturated hydrocarbons having from 4 to about 9 carbon atoms are catalytically nitrogenated in the presence of oxygen at an elevated temperature to produce cyclic imides such as N-substituted and unsubstituted maleimide and dinitriles such as fumaronitrile and maleonitrile. The source of nitrogen is ammonia, or in the case of N-substituted maleimide production, a primary amine.
Cyclic imides such as maleimide are produced by several methods. U.S. Pat. No. 3,960,887 to Renard discloses the production of N-substituted maleimides by reacting maleic anhydride and a primary amine in a solvent for the anhydride and amine under a pressure of from 1 to 5 bars and at a temperature of from 40.degree. C. to 130.degree. C.
U.S. Pat. No. 3,397,210 to Michalowicz discloses a process for producing maleimide or a substituted maleimide by reacting in the vapor phase, ammonia or a primary amine which maleic anhydride in the presence of an acidic alumina containing catalyst.
U.S. Pat. No. 3,899,509 to Riemenschneider discloses a continuous, recycle type process for the manufacture of maleic acid imide from pure or hydrocarbon-mixed maleic anhydride and ammonia by reacting the components in the gaseous phase, in the presence of a dehydration catalyst (alumina). These prior art methods are complex, and costly.
Cyclic imides such as maleimide are useful as monomers and comonomers in the production of high impact strength copolymers. U.S. Pat. No. 3,721,724 to Uebele et al. and assigned to our common assignee herein discusses the marked improvement in ASTM heat distortion temperatures exhibited by copolymers containing acrylonitrile, styrene and butadiene when substituted or unsubstituted maleimide was incorporated in the copolymer. N-substituted maleimides have been used as antibacterial and antifungal agents.
Dinitriles are conventionally produced by reacting dichloro-substituted hydrocarbons with NaCN, or by dimerizing unsaturated mononitriles of one-half the desired carbon number. Dinitriles are useful as comonomers for the production of polymers, and dinitriles are also hydrogenated to form diamines which are used as monomers in polyamide polymers.
The preparation of dinitriles as generally commercially practiced requires the use of corrosive halides and NaCN, while the preparation of cyclic imides such as maleimide is not practiced on a wide scale, due to the complexity of the known preparation processes, low yields of product obtained, and relatively high cost of raw material feedstock.
U.S. Pat. No. 4,070,393 describes the ammoxidation of alkyl-substituted hydrocarbons to produce nitriles and dinitriles utilizing conventional ammoxidation catalysts.